A semiconductor manufacturing process enables simultaneous inclusion of low-voltage and high-voltage devices in a semiconductor device. Generally, the low-voltage device is used as a high-speed and high-performance device, and the high-voltage device is used for input and output. As such a semiconductor device is miniaturized for large capacity and high integration, it becomes necessary to protect the semiconductor device from electrostatic discharges. To this end, an electrostatic discharge protection device should be manufactured together with the low-voltage and high-voltage devices.
However, when the electrostatic discharge protection device is separately formed, an additional ion implantation process using an additional mask is required. These additions increase manufacturing costs. Furthermore, the electrostatic discharge protection device may cause a capacitance increase at the junction and may lead to higher leakage currents, which degrades the reliability of the semiconductor device.